The patent literature includes a great variety of sprinklers. Of particular relevance to the present invention are "pop-up" sprinklers and "gear" sprinklers which are exemplified by the following U.S. Pat. Nos.: 4,625,914; 4,892,252; 4,784,325; 3,955,764; 4,026,471; 4,220,283; 4,234,125; 4,253,608; 4,316,579; 4,351,477; 4,417,691; 4,972,993; 4,681,260.